Gen Nav Problem

[proxus]

*An aircraft at FL350 is required to cross a VOR/DME facility at FL110 and to commence descent when 100 NM from the facility. If the mean GS for the descent is 335 kt, the minimum rate of descent required is:


Correct answer : 1340 FT/MIN
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I cannot seem to find the way to calculate this !! WHY ??

Can anyone point out the "how" in this example.

Thanks in advance.

Proxus

If you are interrested I have another one that I can't complete:
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An aircraft is flying TAS 180 knots and tracking 090°T. The W/V is 045/50. How far can the aircraft fly out from its base and return within 1 hour?



Correct answer : 85 nm
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>> here's yet another one I can't figure out:

*An aircraft at FL330 is rerquired to commence descent when 65 NM from a VOR and to cross the VOR at FL100. The mean GS during the descent is 330 kt. What is the minimum rate of descent required?



Correct answer : 1950 FT/MIN